1. Field of the Invention
The invention relates to a method for monitoring transportation processes for conveying bills and to a self-service terminal having an apparatus carrying out the method. In particular, the invention relates to a method for monitoring the transportation processes for conveying banknotes and checks in a self-service terminal, particularly an automated teller machine.
2. Description of the Related Art
In an automated teller machine, but also in other self-service terminals, such as direct payment cash systems, the accepted or dispensable bills (banknotes, checks, vouchers, etc.) need to be transported safely and reliably, e.g. from the banknote store to the dispensing shaft of the automated machine. In particular, it is necessary to ensure that the bills are transported individually and do not overlap or overlie one another during transport. Each transported bill needs to be able to be sensed exactly in order to be able to ensure particularly that the different note values are counted and sorted. In order to sense the bills and in order to control the transport system, the bills are usually routed, according to their length, through at least one light barrier. Each light barrier has at least one light-sensitive sensor that reacts to optical state changes (light-dark or dark-light). Hence, particularly the start (front edge) and/or the end (rear edge) of the individual bill can be detected. An apparatus for handling and transporting bills is described in DE 10 2010 004580 A1, for example. The conventional optical scanning of bills can lead to problems when individual bills have viewing windows that are provided as additional security features. The reason is that the appearance of viewing windows during scanning of the bills leads to multiple state changes being reported in succession, as a result of which it may be difficult to detect the front and/or rear edge of the respective bill exactly.
WO 03/023 724 A2 describes a detection system for optical media in the form of banknotes and other bills. The system is conditioned to detect or to identify viewing windows, that is to say transparent areas, in the bills as well. To this end, a light barrier system is installed that has an optical transmitter and two light-sensitive sensors that are arranged at different positions. While the respective bill is passing through, one sensor identifies the light reflected by the bill; the other sensor identifies the light passing through as soon as a window appears. Hence, the appearance of the various edges, namely the front and rear edges, on the one hand, and any window edges, on the other hand, can be detected. However, this solution is reliant on the windows that appear having sufficiently good transparency, which is not always the case. The transparency of the windows may be very low on account of soiling of the bills or on account of windows that are consciously kept semipermeable or opaque and/or colored. Should windows with low transparency appear, reflections can even result in a window edge being incorrectly detected as a front or rear edge of a bill, and therefore in the control of the transport system operating erroneously.
Further prior art is disclosed in U.S. Pat. No. 5,455,659 A, EP 0 080 158 A2, EP 0 884 652 A2. In addition, the article “Prepunched Paper Feed” by D. R. Blankenship et al, which appeared in the IBM Technical Disclosure Bulletin, Vol. 25, May 1983, on pages 6524-6526, describes a method for safe paper feed for prepunched copy paper.
It is therefore an object of the present invention to provide a method for monitoring transportation processes for bills that ensures reliable control of the transportation processes even for such bills as have windows.